/Engine/Source/Runtime/Engine/Classes/Animation/AnimInstance.h
Play normal animation asset on the slot node by creating a dynamicUAnimMontagewith blend in arguments. You can only play one asset (whether montage or animsequence) at a time per SlotGroup.
[UAnimMontage](API\Runtime\Engine\Animation\UAnimMontage) * PlaySlotAnimationAsDynamicMontage_WithBlendArgs ( [UAnimSequenceBase](API\Runtime\Engine\Animation\UAnimSequenceBase) * Asset, [FName](API\Runtime\Core\UObject\FName) SlotNodeName, const [FAlphaBlendArgs](API\Runtime\Engine\FAlphaBlendArgs) & BlendIn, const [FAlphaBlendArgs](API\Runtime\Engine\FAlphaBlendArgs) & BlendOut, float InPlayRate, int32 LoopCount, float BlendOutTriggerTime, float InTimeToStartMontageAt )